1. Field of the Invention
This invention relates to apparatus used to in connection with the servicing of wellbores (namely, those of oil and gas wells), including the treatment of fluids in the wellbore, including but not limited to “clear” (that is, non-solids bearing) completion fluids in the wellbores, solids-bearing drilling muds, or any other fluids. More specifically, this invention relates to an apparatus run downhole on a workstring, which catches solids (including not only solids from drilling muds, debris such as cement, milled up downhole tools, but solids remaining from drilling mud, etc.) entrained in the fluids and permits removal of the solids from the wellbore.
2. Related Art
In the drilling and completion of oil and gas wells, a number of situations arise in which solids are present in the wellbore fluid, and removal of the solids is necessary. As an example, during the drilling and/or completion of a well, with drilling mud (that is, solids-bearing drilling mud), solids such as cement particles, pieces of downhole equipment which have been drilled and/or milled, junk lost in the hole, etc. may become present in the mud. Some way to remove such solids is necessary, or at a minimum desired.
In other situations, certain types of oil and gas well completions depend on the use of a solids-free (or as nearly solids free as possible) completion fluid. Such completion fluids, sometimes referred to as completion brines, for example calcium bromide, have densities higher than that of fresh water, due to the salts dissolved therein. Gravel pack completions are an example of a well completion procedure which requires the use of clear completion fluids. In the typical sequence of drilling and completing a well, the drilling of the well generally utilizes drilling mud, which is solids laden. Once the drilling is complete and completion casing is run, the drilling mud is displaced from the wellbore, and a clear completion fluid placed in the wellbore. Some solids from the drilling mud invariably end up in the completion fluid, e.g. from a layer of mud on the interior of the casing string, from surface tanks, etc. It is important to remove as many of such solids as possible, because the completion efficiency of the well can be seriously and adversely impacted if solids remain in the completion fluid. For example, a gravel pack completion can be partially, if not completely, plugged by solids entrained in the completion fluid. As a result, there exists an incentive to clean completion fluids to the greatest extent possible, by removing as many solids as possible.
Therefore, regardless of the type of fluid in a wellbore, it may become desirous to remove solids entrained therein. Various apparatus and methods have been developed in the past to do so, however the prior art apparatus and methods known to applicants have various limitations. The present invention seeks to address such limitations and provide an effective means to trap and remove solids from wellbore fluids.